Restless Leg Syndrome (RLS) is characterized by a recurring irresistible urge to move the legs, usually to relieve discomfort. The etiology of RLS is complex, but clinical evidence favors involvement of dopaminergic neural activity especially given the partial therapeutic efficacy of dopamine agonists. Furthermore, iron (Fe) deficiency has been reported in the brains of some familial and non-familial RLS cases. Notably, alterations in serum and brain Fe status have been strongly associated with reciprocal changes in body and brain manganese (Mn) status. Genome wide association studies have implicated common variants in at least two genes (MEIS1 and BTBD9) to be associated with more than a 50% increase risk for RLS. This competing renewal application seeks to establish a Virtual Consortium for Translational/Transdisciplinary Environmental Research (ViCTER), to test the hypothesis that RLS is associated with alterations in systemic and neuronal Mn status that are influenced by RLS genetic risk loci. We will evaluate gene-environment interactions between Mn exposure and neuronal Mn status with genetic risk factors for RLS expanding the scope of the parent R01, which explores mechanisms of Mn neurotoxicity of the dopaminergic system and identifies modifiers of cellular Mn status in the context of Parkinson's disease (PD) and PD genetic risk factors.
In Specific Aim 1, we will test the hypothesis that RLS patients will exhibit elevated brain and/or serum Mn levels influenced by the patients Fe status and inheritance of genetic risk factors (e.g. common variants of MEIS1 and BTBD9).
In Specific Aim 2, we will test the hypothesis that lymphocytes isolated from RLS patients will exhibit Fe-deficiency related phenotypes and alteration in cellular Mn levels modulated by their RLS genetic risk status.
In Specific Aim 3, we will identify the functional relationship between meis1 and btbd9 knockdown in worms with Mn and Fe loads, and the ability of small molecules to rescue C. elegans from the RLS phenotype.
In Specific Aim 4, we will test the hypothesis that dopaminergic neuronal progenitors differentiated from induced pluripotent stem cells (iPSCs) derived from RLS patients will exhibit differences in Mn transport biology influenced by common variants in MEIS1 and BTBD9. The seamless organizational structure and the researchers'enthusiasm ensures that this innovative ViCTER will provide insight into both basic biology and the mechanistic events leading to RLS, develop techniques that will provide opportunities to understand and reduce RLS, and assesses genomic information to make better-supported individual decisions about diagnosis and treatment that are tailored to the biology of the specific patient.

Public Health Relevance

Restless Legs Syndrome (RLS) is one of the most common neurological disorders and as many as 10% of the United Sates population may have RLS, with moderate to severe RLS affecting 2-3% of adults. The proposed studies will (1) provide novel information on the role of manganese (Mn) in the etiology of RLS, (2) delineate gene- environment interactions within and across species that hasten the development of RLS, and (3) identify potential therapeutic modalities for this syndrome. Overall, the principal investigators seek to test the hypothesis that RLS is associated with alterations in systemic and neuronal Mn status that are influenced by RLS genetic risk loci.